Researchers
have solved the mystery of 4 million square miles of dark region in the
northern lowlands in Mars: the dark areas of the Red Planet are made from
glass.

Briony Horgan and Jim Bell of Arizona State University in Tempe
analysed near-infrared spectra of the regions, gathered by the Mars
Express orbiter. They found absorption bands characteristic of the iron
in volcanic glass, a shiny substance similar to obsidian that forms
when magma cools too fast for its minerals to crystallise.